The selection of combined heat and power plants (CHP) is quite large, as is the high variance of different plant types. The distinction is manufactured by the generated power/heat output on the main one hand and by the energy source used on another. For several CHP plants, numerous physical parameters are measured, evaluated and monitored to guarantee the longest possible service life. This article offers information regarding which measuring instruments and principles this can be achieved with.
Combined heat and power plants ? environment-friendly power generators
In contrast to the original boiler or condensing boiler, the CHP plant generates both electricity and heat. Thus, CHP plants make an important contribution to environment-friendly energy generation.
Wide variety of applications
The versatile application possibilities, from single or multi-family dwellings, through industrial and commercial, public facilities, around large district/local heat utilities and also biogas plants, require the application of completely different measuring instruments. Key factors are: functionality, quality, long service life, fast availability and services. The price/performance ratio plays a particular role in any system ? large or small.
The physical measurands
Small nano plants from 1 kWel, micro and mini plants from 2.5 to 15-50 kWel, and in addition large plants around 4,500 kWel need the proper measuring instruments for high efficiency and environment-friendly energy generation. The measurands pressure, temperature and level are dominant. The energy source should be considered when choosing the instruments. The number of marking points in the schematic illustration of a CHP plant helps it be clear: There is much to monitor to assure the longest possible service life.
Schematic illustration of a combined heat and power plant incl. measuring points
Monitoring and control tasks
The measuring instruments used fulfil important monitoring and control tasks and are generally electronic measuring instruments. They also enable remote monitoring.
For measuring the temperature, screw-in, insertion and contact probes are installed, matched to the design and the space available. On heat exchanger, in the heating and cooling circuits and also for measuring the engine oil temperature, Pt100, Pt1000, KTY and NTC measuring elements are used. With large plants, temperatures on the exhaust pipe and on the cylinder head are monitored using thermocouples. This enables conclusions to be produced concerning the effectivity of the engine.
Pressure switches and pressure sensors are accustomed to control the oil pressure and the pressure in the cooling water circuit. As well, they also fulfil a safety function. If you can find any deviations between the SET and ACTUAL value, according to the concept, either a warning signal is triggered or the engine is switched off.
To monitor the oil level, depending on the size of the system, between one and three float switches are installed. Particularly in Placid , the sometimes quite strong vibrations pose challenging for the measurement technology. Using optoelectronic level switches that tolerate high temperatures and that are not harmed, even by strong shocks, is therefore ideal. The respective level switch monitors the oil level in a reservoir and signals when the oil level drops too low.
Conclusion
The large numbers of measuring points and the widely differing measuring tasks require close cooperation between your CHP plant manufacturer and the manufacturer of the measurement technology. Therefore, Exasperated is worth ? both technically and economically ? choosing a supplier who offers everything from one source.
Note
WIKA offers a large collection of reliable measuring instruments for pressure, temperature and level. You could find selected products for your CHP plant on the WIKA website in the Combined heat and power plants section. Do you need support with the compilation of one’s measuring instrument package for the CHP plant? Your contact person will undoubtedly be happy to assist you to.